Method of pattern formation using ultrahigh heat resistant positive photosensitive composition

ABSTRACT

In the process wherein a high heat resistance is required for a photoresist pattern such as a manufacture of a TFT active matrix substrate, a super high heat resistant positive pattern is formed using a positive-working photosensitive composition. The pattern forming method of the present invention comprising steps of: applying a photosensitive composition onto a substrate comprising (a) an alkali-soluble resin, (b) a photosensitizer having a quinone diazide group, (c) a photo acid generator, (d) a crosslinking agent and (e) a solvent; then exposing the substrate to light through a mask; forming a positive image by developing and removing the exposed area to light; exposing a whole area of the positive image to light; and post-baking, if necessary. In the case of using 1,2-naphthoquinone-4-sulfonyl compound as the photosensitizer having a quinone diazide group, the above component (c) can be omitted since this compound also functions as a photo acid generator of the component (c).

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a photoresist pattern forming method tobe used upon manufacturing a semiconductor device, a flat panel display(FPD) and so on, and particularly to a method for forming a super highheat resistant resist pattern which is suitable for a 4 mask processusing a half tone mask (a resist pattern forming method using reducednumber of photo-masks), that is one of the methods of a TFT (Thin FilmTransistor) active matrix manufacturing process requiring a high heatresistant property of a photoresist or for a formation of a corrugatedreserve material for a reflective-type of TFT.

BACKGROUND ART

In the various fields such as manufacture of semiconductor integratedcircuits such as LSI, production of a display face of FPD, manufactureof a circuit substrate of a thermal head and so on, photolithographictechnology has so far been employed for forming microelements or forconducting fine processing. In the photolithographic technology, apositive- or negative-working photosensitive composition is used to forma resist pattern. Of these photosensitive compositions, a compositioncomprising an alkali-soluble resin and a compound containing a quinonediazide group is widely used as a positive-working resist. Thiscomposition is described with a various kind of compositions in a lot ofliteratures (patent literature Nos. 1 to 4 to be referred below, forexample) as “novolak resin/quinone diazide compound”, for example.Research and development works have so far been conducted for thesecompositions comprising an alkali-soluble resin and a compoundcontaining a quinone diazide group from the viewpoints of both a novolakresin and a photosensitizer.

[Patent Literature No. 1]

Japanese examined patent publication number Sho. 54-23570 (page-1)

[Patent Literature No. 2]

Japanese examined patent publication number Sho 56-30850 (page-1)

[Patent Literature No. 3]

Japanese laid-open patent publication number Sho 55-73045 (page-1 to 4)

[Patent Literature No. 4]

Japanese laid-open patent publication number Sho 61-205933 (page-1, 3 to5)

On the other hand, altogether 5 pieces or more of photo masks have sofar been used in the array substrate manufacturing process of TFT activematrix substrate. However the application of a higher number of maskscauses a tendency of high manufacturing cost, a tendency to require along time of process time, and a lower yield upon manufacturing. Inorder to solve the problem, a process using a small number of masks,i.e. a 4-mask process is being examined. And then a manufacturing methodof a liquid crystal display device of high aperture ratio to use a smallnumber of photo masks is already being proposed as referred to patentliterature No. 5, for example.

[Patent Literature No. 5]

Japanese laid-open patent publication number 2002-98996 (page-2 to 5)

In mask saving process described above, generally the processes offorming a resist pattern with a step by half-tone exposure to light andof making dry-etching are required. Therefore heat treatment for aphotoresist pattern is conducted in order to improve a dry-etchingresistance of a resist film upon the dry-etching. The heat resistanttemperature required at this stage is generally 130° C. or higher andthen there is a problem of pattern deterioration in the heating processfor the positive-working photoresist so far being applied. For thatreason, an improved process such as a manufacture by the method applyingmilder etching condition or an improvement of heat resistance ofpositive-working photoresist materials are required.

In the case of a reflective type of TFT, it is necessary to prepare areserve material with a shape such as a corrugated shape, followed byspattering to cover thereon with a high light reflective metal such asaluminum. In this process, in order to control water absorption or metalion migration, or in a manufacturing process of a reflective type of TFTpanel, the reserve material with corrugated shape is exposed to organicsolvents such as MIBK (methyl isobutyl ketone), THF (tetrahydrofuran),NMP (N-methyl-2-pyrrolidone) and so on. Therefore post-baking isrequired in order to provide the reserve material with a resistance tothose solvents. However a positive-working photoresist so far beingapplied is likely to flow when post-baked at 130° C. or higher and thenthere is a problem to get out of a necessary original corrugated shape.

Referring to the situation described above, an object of the presentinvention is to provide a pattern forming method using apositive-working photosensitive composition by which a good and superhigh heat resistant positive pattern can be formed in a process whereina high heat resistance of a photoresist pattern is required such asmanufacturing a TFT active matrix substrate.

The present invention also has an object to provide a pattern formingmethod using a positive-working photosensitive composition by which apattern having a good and super-heat resistance pattern with steps orcorrugated pattern can be formed using a half tone mask in a processwherein a high heat resistance of a photoresist pattern is required suchas manufacturing a TFT active matrix substrate.

DISCLOSURE OF THE INVENTION

As a result of eager studies and examinations, the present inventorsfound that the above-described object can be attained by using aspecific positive-working photosensitive composition, exposing a wholearea to light after exposure to light and development thereof, and ifnecessary heat-treating (post-baking) to reach to the present invention.

It means that the present invention relates to a pattern forming methodwhich is characterized in comprising [1] a step of applying on asubstrate material a photosensitive composition comprising (a) analkali-soluble resin, (b) a photosensitizer having a quinone diazidegroup, (c) a photo acid generator, (d) a crosslinking agent and (e) asolvent to form a photosensitive layer, [2] a step of exposing thephotosensitive layer to light through a mask, [3] a step of removing theexposed area of the photosensitive layer by development to form apositive image, and then [4] a step of exposing a whole area of thephotosensitive layer to light.

The present invention also relates to a pattern forming method describedabove which is characterized in that in the pattern forming method, aphotosensitizer having a quinone diazide group (b) and a photo acidgenerator (c) have an absorption activity at the same exposurewavelength and a whole area exposure is conducted at the exposurewavelength where both said photosensitizer and said photo-acid generatorhave an absorbing activity.

Furthermore the present invention relates to a pattern forming methodwhich is characterized in comprising [1] a step of applying on asubstrate material a photosensitive composition comprising (a) analkali-soluble resin, (f) a compound having a quinone diazide group andfunctioning as a photosensitizer and a photo-acid generator, (d) acrosslinking agent and (e) a solvent to form a photosensitive layer, [2]a step of exposing the photosensitive layer to light through a mask, [3]a step of removing the exposed area of the photosensitive layer bydevelopment to form a positive image, and [4] a step of exposing a wholearea of the positive image to light.

The present invention also relates to a pattern forming method accordingto any one of above described pattern forming methods, which ischaracterized in that after the step of exposing the whole area of thephotosensitive layer to light, [5] heat treatment (post-baking) iscarried out.

The present invention also relates to a pattern forming method accordingto any one of above described pattern forming methods, which ischaracterized in that the alkali-soluble resin is at least one speciesselected from the group consisting of novolak resins, polyvinyl phenolresins and acrylic resins.

The present invention also relates to a pattern forming method accordingto any one of above-described, pattern forming methods, which ischaracterized in that the mask used at the exposure step describedbefore is a mask having a half-tone region which is partially made 10 to90% of transmittance at a light transmission region by being equippedwith a semi-transparent film or installing a slit or a mesh having adimension of not more than a resolution of the exposure device.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows an example, of a mask having a half tone region.

DETAILED EXPLANATION OF THE INVENTION

Hereinafter, the present invention will be further described in moredetail.

A novolak resin which is used in the photosensitive composition of thepresent invention may be any one of novolak resins which are used in aphotosensitive composition containing an alkali-soluble resins and aphotosensitizer having a quinone diazide group so far publicly known andis not particularly limited. The novolak resin which is preferably usedin the present invention is obtained by polycondensing one kind ofphenols or a mixture of plural kinds thereof with aldehydes such asformalin.

As phenols constituting said novolak resin, there may be illustratedwith, for example, phenol, p-cresol, m-cresol, o-cresol,2,3-dimethylphenol, 2,4-dimethylphenol, 2,5-dimethylphenol,2,6-dimethylphenol, 3,4-dimethylphenol, 3,5-dimethylphenol,2,3,4-trimethylphenol, 2,3,5-trimethylphenol, 3,4,5-trimethylphenol,2,4,5-trimethylphenol, methylene-bisphenol, methylene-bis p-cresol,resorcinol, catechol, 2-methylresorcinol, 4-methylresorcinol,o-chlorophenol, m-chlorophenol, p-chlorophenol, 2,3-dichlorophenol,m-methoxyphenol, p-methoxyphenol, p-butoxyphenol, o-ethylphenol,m-ethylphenol, p-ethylphenol, 2,3-diethylphenol, 2,5-diethylphenol,p-isopropylphenol, a-naphthol, β-naphthol, and the like. These are usedsingly or as a mixture of two or more kinds thereof.

As aldehydes, there may be illustrated with paraformaldehyde,acetaldehyde, benzaldehyde, hydroxybenzaldehyde, chloroacetaldehyde andso on besides formalin. These are used singly or as a mixture of two ormore kinds thereof.

The weight average molecular weight of the novolak resin used in thephotosensitive composition of the present invention, as determined bypolystyrene standards, is preferably 5,000 to 100,000, more preferably5,000 to 50,000.

An alkali-soluble resin may be illustrated with a vinyl phenol type ofresin, or an acrylic type of resin besides a novolak resin. As thealkali-soluble acrylic type of resin, there are exemplified a copolymerof unsaturated carboxylic acid such as acrylic acid or methacrylic acidand acrylic esters and/or methacrylic esters.

As the photosensitizer containing a quinone diazide group which is usedfor the photosensitive composition of the present invention, anyphotosensitizer containing a quinone diazide group can be used andparticularly one obtained by a reaction between quinone diazide sulfonicacid halide such as naphthoquinone diazide sulfonic acid chloride orbenzoquinonediazide sulfonic acid chloride and low or high molecularweight compounds containing functional groups which can be condensedwith these acid halides is preferred. As functional groups which can becondensed with these acid halides, a hydroxyl group or an amino groupcan be exemplified and the hydroxyl group is particularly preferred. Aslow molecular compounds containing a hydroxyl group, there areexemplified hydroquinone, resorcinol, 2,4-dihydroxybenzophenone,2,3,4-trihydroxybenzophenone, 2,4,6-trihydroxybenzophenone,2,4,4′-trihydroxybenzophenone, 2,3,4,4′-tetrahydroxybenzophenone,2,2′,4,4′-tetrahydroxybenzophenone, 2,2′,3,4,6′-pentahydroxybenzophenoneand so on.

Examples of the high molecular compounds containing a hydroxyl groupinclude novolak resin and polyvinylphenol and so on. A reactant betweenqunione diazide sulfonic acid halide and a compound having a hydroxylgroup may be single kind of a esterified compound or a mixture of two ormore kinds having different esterification ratios. The photosensitizercontaining a quinone diazide group of the present invention is usedpreferably at 1 to 30 parts by weight relative to 100 parts by weight ofthe resin components in the photosensitive composition.

The photo acid generator (a compound generating an acid by irradiationof radiation) which is used in the photosensitive composition of thepresent invention may be any compound generating an acid by irradiationof radiation. These compounds may be preferably illustrated with one sofar used as a photo acid generator in a chemically amplified resist. Asthese photo acid generators, there may be illustrated an onium salt suchas iodonium salt, sulfonium salt, diazonium salt, ammonium salt,pyrridinium salt and so on, a compound containing halogen such ashydrocarbon compound containing a haloalkyl group, heterocyclic compoundcontaining a haloalkyl group (for example, halomethyl triazinederivative and so on), diazoketone compound such as 1,3-diketo-2-diazocompound, diazobenzoquinone compound, diazonaphthoquinone compound,sulfone compound such as β-ketosulfone, β-sulfonylsulfone and so on, andsulfonic acid compound such as alkylsulfonic ester, haloalkylsulfonicester, aryl sulfonic ester, iminosulfonate, and so on. These can be usedsingly or as a mixture of two or more kinds thereof.

Examples of photo acid generators which are particularly preferably usedin the photosensitive composition of the present invention includes atriazine type of acid generator represented by2-[2-(5-methylfuran-2-yl)ethenyl]-4,6-bis-(trichloromethyl)-s-triazineor a cyano type of acid generator represented by5-methylsulfonyloxyimino-5H-thiophene-2-ylidene-2-methylphenylacetonitrile. The formulated amount of the photo acid generator isusually 0.05 to 9 parts by weight relative to 100 parts by weight of analkali-soluble resin, preferably 0.5 to 3.0 parts by weight.

Furthermore when 1,2-naphthoqinonediazidesulphonyl compound is used as acompound containing a quinone diazide group, this compound works as aphotosensitizer as well as a photo acid generator and therefore it ispossible to use one substance as the above described (b) and (c)components.

As the crosslinking agent used in the present invention, there may beany one which crosslinks and hardens an alkali-soluble resin byreceiving an action of an acid which is generated at an area irradiatedby radiation and not particularly be limited. As the crosslinkingagents, there may be raised a various kind of crosslinking agents suchas a melamine-, benzoguanamine- or urea-type of crosslinking agent, amulti-functional epoxide group containing compound and so on.

As low molecular crosslinking agents among melamine, benzoguanamine andurea types of crosslinking agents, there are exemplified methylolatedmelamines or alkyl ethers thereof such as hexamethylol melamine,pentamethylol melamine, tetramethylol melamine, hexamethoxymethylmelamine, pentamethoxymethyl melamine, or tetramethoxymethyl melamine,methylolated benzoguanamines and alkyl ethers thereof such astetramethylol benzoguanamine, tetramethoxymethyl benzoguanamine, ortrimethoxymethyl benzoguanamine, N,N-dimethylol urea or dialkyl etherthereof, 3,5-bis(hydroxymethyl)perhydro-1,3,5-oxadiazine-4-on(dimethylol urone) or alkyl ether thereof, tetramethylolglyoxaldiureineor tetramethylol ether thereof, 2,6-bis(hydroxymethyl)4-methylphenol oralkyl ether thereof, 4-tert-butyl-2,6-bis(hydroxymethyl)phenol or alkylether thereof, and5-ethyl-1,3-bis(hydroxymethyl)perhydro-1,3,5-triazine-2-on(N-ethyldimethylol triazone) or alkyl ether thereof as preferable ones.

As high molecular crosslinking agents among melamine, benzoguanamine andurea types of crosslinking agents, there are exemplified alkoxyalkylatedamino resins such as alkoxyalkylated melamine resins, alkoxyalkylatedurea resins, which can be exemplified with methoxymethylated melamineresins, ethoxymethylated melamine resins, propoxymethylated melamineresins, butoxymethylated melamine resins, methoxymethylated urea resins,ethoxymethylated urea resins, propoxymethylated urea resins, andbutoxymethylated urea resins as a preferable one. A multi functionalepoxide group containing compound represents a compound which containsone or more of benzene ring or heterocyclic ring in a molecule andbesides two or more of epoxide groups.

As a solvent which is applied in the present invention, there areillustrated ethylene glycol monoalkyl ethers such as ethylene glycolmonomethyl ether, ethylene glycol monoethyl ether, etc.; ethylene glycolmonoalkyl ether acetates such as ethylene glycol monomethyl etheracetate, ethylene glycol monoethyl ether acetate, etc.; propylene glycolmonoalkyl ethers such as propylene glycol monomethyl ether, propyleneglycol monoethyl ether, etc.; propylene glycol monoalkyl ether acetatessuch as propylene glycol monomethyl ether acetate, propylene glycolmonoethyl ether acetate, etc.; lactic esters such as methyl lactate,ethyl lactate, etc.; aromatic hydrocarbons such as toluene, xylene,etc.; ketones such as methyl ethyl ketone, 2-heptanone, cyclohexanone,etc.; amides such as N,N-dimethylacetamide, N-methylpyrrolidone (NMP),etc.; lactones such as γ-butyrolactone, and the like. These solvents maybe used singly or as a mixture of two or more kinds thereof.

In the photosensitive composition of the present invention there may beincorporated, if necessary, adhesion aids, surfactants and so on.Examples of the adhesion aids include alkylimidazolines, butyric acid,alkyl acids, polyhydroxystyrene, polyvinyl methyl ether, t-butylnovolak,epoxysilane, epoxy polymers, silanes and so on and examples of thesurfactants include nonionic surfactants such as polyglycols and thederivatives thereof, i.e., polypropylene glycol or polyoxyethylenelauryl ether, and so on; fluorine-containing surfactants such as Fluorad(trade name; product of Sumitomo 3M Co., Ltd.), Megafac (trade name;product of Dai-nippon Ink & Chemicals, Inc.), Surflon (trade name;product of Asahi Glass Company, Ltd.) and organosiloxane surfactantssuch as KP341 (trade name; product of Shin-Etsu Chemical Co., Ltd).

By the way, in Japanese Patent publication laid open No. Hei 6-35183(1994), there is described a color filter preparation method using acomposition for forming a color filter comprising a hardenable resin byacid, a quinone diazide compound, a crosslinking agent, a photo acidgenerator, a dye and a solvent. This method has an object to obtain acolor filter being excellent in resolution, heat resistance and so on.However the composition is neither one which realizes a high resolutionand a super high heat resistance which are required in manufacturing ofa semiconductor or TFT and so on such as the present invention nor onewhich can form a pattern having a various kind of shape or profile, forexample step form, corrugated shape and so on according to the objectsuch as the present invention. The reason thereof is assumed as follows.It means that in the composition for forming a color filter describedbefore, since dyes are used as one of film forming components, aradiation used upon pattern-wise exposure to light is absorbed by thedyes. As the radiation does not reach to the bottom of the film soreduce a resolution. In the composition for forming a color filterdescribed before, it is not an obstacle to obtain a pattern having adimension of a few hundred microns required for a color filter, howeverthe composition is not able to be applied to a pattern formationrequired for manufacturing a semiconductor or TFT array which requires aresolution of from a few tens to a few microns or sub microns. And alsoupon a whole area exposure to light, since a radiation is absorbed onthe way to the bottom of the film of the composition, a necessary acidis not generated on the bottom area of the film. Therefore thecomposition is not sufficiently crosslinked and in the result a heatresistance of the film is reduced. Furthermore dyes are likely to have ahigh sublimation property. When the dyes are removed from the film, notonly it contaminates the equipments in the process but also the filmitself becomes micro porous to deteriorate a resistant property tosolvents or to a etching liquid. Even if it is not a sublimated dye, asa heat resistant property of the dye is low, a heat resistant propertyof film is reduced. The present invention does not use dyes even as anoptional component. It is, therefore, essentially different from thecomposition for forming a color filter described before and then itbecomes possible to realize a resist pattern having a high resolutionand a super high heat resistance which are required in a manufacturingof a semiconductor or TFT and so on.

The pattern forming method of the present invention will be indicatedthrough processes. First the photosensitive composition described beforeis applied on a substrate material such as a silicon wafer or a glasssubstrate and so on by spin coating or slit coating and so on. Thesubstrate material may be ones wherein a silicon oxide film, a metalfilm such as aluminum, molybdenum, and chromium, a metal oxide film suchas ITO, furthermore a semiconductor element or a circuit pattern areinstalled onto the surface of the substrate material if necessary. Thecoating method is not limited to the ones described before concretelybut can be any coating methods so far applied when applying aphotosensitive composition. After applying a photosensitive compositionon a substrate material, the substrate is heated up to the temperaturebetween 70° C. and 110° C. by a convection type of oven or a hot plateand so on (pre-baking), a solvent component therein is removed to form afilm of the photosensitive composition described before on a substratematerial. This substrate material is exposed to light for patterningthrough a desired mask. A wavelength of an exposure to light at thistime may be any one such as a single wavelength such like g-line (436nm), h-line (405 nm), i-line (365 nm), KrF (248 nm), ArF (193 nm), amixed wavelength of g-line and h-line or a mixture of g-line, h-line andi-line called “broad band” which are applied so far upon exposing aphotosensitive composition to light.

After the pattern-wise exposure to light, an exposed area is dissolvedout by developing with an alkali developer and only an unexposed area isremained to provide with a positive pattern. The alkali developer isusually aqueous solution of a quaternary amine salt such astetramethylammonium hydroxide and so on or an aqueous solution of aninorganic hydroxide such as sodium hydroxide or potassium hydroxide. Thereason why the exposed area is dissolved out into the alkali developerand the unexposed area is remained on a substrate is that aphotosensitizer having a quinone diazide group of the component (b) ischanged to a carboxylic acid by the exposure to light and the carboxylicacid is alkali-soluble. At the same time although an acid is generatedfrom an acid generator of the component (c) at the exposed area, thisacid itself hardly influence on a pattern-wise exposure to light.

Next a whole area exposure to light at the same wavelength as one usedupon the patterning exposure to light by not using a mask or by using ablank mask (all light pass through) is conducted on the patterningsubstrate where a development is completed. After the whole areaexposure to light is completed, the substrate material is heated at thetemperature of 110° C. to 160° C. by a convection type of oven or a hotplate and so on (post-baking) to make the film baked and solidified.Herewith the unexposed area upon a first patterning exposure to light isexposed to light, and an acid is generated from an acid generator of thecomponent (c) in the unexposed are. By the catalytic action of the acid,a crosslinking reaction is caused between an alkali-soluble resin of thecomponent (a) and a crosslinking agent of the component (d) to form ahard film.

Since the crosslinking is conducted by getting the heat of post-baking,a base resin becomes solidified by keeping a shape formed by developmentwithout flowing. Although there happened a problem such that a patternwas likely to become deteriorated or rounded when the positive-workingphotosensitive composition so far applied and the process so far appliedare used and the pattern formed thereby is heated at about 120° C. orhigher, such phenomenon does not happen in the present invention.Furthermore according to the present invention, a high heat resistanceafter post-baking can be realized not only for an usual pattern such asa line and space pattern, a dotted pattern or a hole pattern but alsofor a patterning containing an uneven (concavity-convex) form which isformed by remaining a resist film in a halfway thickness using a maskhaving a partial half tone parts or for a patterning of a corrugatedshape.

The half tone parts described before in the mask can be formed, forexample either by putting (installing) a semi-light-transmissible filmwhich is prepared by, for example, amorphous silicon film, siliconnitride film or chromium film having an adequate thickness onto thedetermined area of the mask or by installing a slit or mesh patternhaving a dimension below a resolution limit of an exposure device ontothe determined area to make a transmittance of a light transmissiblearea from 10% to 90%. When forming a pattern having a corrugated shape,a line and a space pattern having a dimension below a resolution limitof an exposure device and in the vicinity of the resolution limit may beinstalled onto a mask, for example.

In the above description, an example of a photosensitive compositioncontaining a photosensitizer and a photo acid generator was shown.However a heat resistant pattern can also be formed in the same processas described above when applying single compound having the functionsboth of a photosensitizer and a photo acid generator in the presentinvention. In addition, in the above description, an example using aphotosensitizer and a photo acid generator which have an absorbingactivity against a same exposure wavelength was shown. In this way whenboth a photosensitizer and a photo acid generator have an absorbingactivity against a same exposure wavelength, a pattern-wise exposure tolight and a whole area exposure to light can be implemented using thesame light-exposure device. Therefore there is no need to prepare twokinds of light-exposure devices in that case and it would be preferable.However a pattern forming method of the present invention is not limitedto this one and it may be the case where a photosensitizer and a photoacid generator do not have an absorbing activity against a same exposurewavelength. In this case, a pattern wise exposure to light and a wholearea exposure to light may be conducted at different light-exposurewavelengths according to photosensitizing wavelengths of aphotosensitizer and a photo acid generator.

BEST MODE FOR PRACTICING THE INVENTION

The present invention will now be described more specifically byreference to Examples which, however, are not to be construed to limitthe instant invention in any way.

SYNTHESIS EXAMPLE 1 Synthesis of a Novolak Resin

100 parts by weight of mixed cresols wherein the ratio ofm-cresol/p-cresol is 6/4, 56 parts by weight of 37% by weight offormaldehyde, and 2 parts by weight of oxalic acid were charged and werereacted at the reaction temperature of 100° C. for 5 hours in theconventional manner. The weight average molecular weight of theresulting novolak resin was 15,200 as determined by polystyrenestandards.

SYNTHESIS EXAMPLE 2 Synthesis of a Photosensitizer

2,3,4-trihydroxybenzophenone and 1,2-naphthoquinonediaizde-5-sulfonylchloride were dissolved in dioxane at 1/2.0 feedingratio (in molar ratio) and were esterified in the conventional mannerusing triethylamine as a catalyst. According to a measurement of theresulting ester by HPLC (High Performance Liquid Chromatography), theester contained 29% diester and 63% triester.

SYNTHESIS EXAMPLE 3 Synthesis of a Photosensitizer and a Photo AcidGenerator, Concurrently

2,3,4-trihydroxybenzophenone and 1,2-naphthoquinonediazide-4-sulfonylchloride were dissolved in dioxane at 1/2.0 feedingratio (in molar ratio) and were esterified in the conventional mannerusing triethylamine as a catalyst. According to a measurement of theresulting ester by HPLC (High Performance Liquid Chromatography), theester contained 25% diester and 61% triester diester

EXAMPLE 1

100 parts by weight of novolak resin obtained by the Synthesis Example1, 17 parts weight of photosensitizer obtained by the Synthesis Example2, 1 part by weight of2-[2-(5-methylfurane-2-yl)ethenyl]-4,6-bis-(trichloromethyl)-s-triazineas a photo acid generator, and 5 parts by weight of Cymel 300(manufactured by Mitsui Cytech) which is methoxymethyl melamine resin asa crosslinking agent were dissolved into propylene glycol monomethylether acetate. After incorporating thereto 500 ppm of a fluorinecontaining surfactant, Fluorad F-472 (manufactured by Sumitomo 3M) inorder to prevent radial wrinkles generated on a resist film upon spincoating, so called striation, the solution was stirred and then filteredthrough a 0.2-μm filter to prepare a photosensitive composition of thepresent invention. This composition was spin-coated on a 4-inch siliconwafer, and pre-baked on a hot plate at 100° C. for 90 seconds to obtaina 3-μm thick resist film. This resist film was pattern-wise exposed tolight by a stepper FX-604F manufactured by Nikon having g+h linesmixture wavelength through a mask and was developed by paddledevelopment method using a 2.38 weight- % aqueous solution oftetramethylammonium hydroxide for 60 seconds. At this time thepattern-wise exposure to light was conducted at an optimal sensitivitywith an exposure energy volume by which a 5-μm line and space patternwith 1:1 ratio of a mask was developed as wide as a mask design. Afterthe development, a section of the 5-μm line and space pattern wasobserved by SEM (Scanning Electronic Microscope). The result was shownin Table 1 (after development). As being obvious from Table 1, arectangular pattern was formed normally.

A whole area exposure to light was conducted on the developed substrateusing the same light-exposure device as one used in the patterninglight-exposure step through a blank mask (all light pass through). Afterthe whole exposure to light, the substrates were heated up on a hotplate up to 120° C., 140° C. or 160° C., respectively for 90 seconds toconduct a post-baking. Each section of patterns was observed by SEMafter post-bakings were conducted at the temperatures described above.The results were shown in Table 1. As shown in Table 1, a rectangularshape was maintained after baking at 140° C., and a top area becameslightly rounded after baking at 160° C. As the result, it was confirmedthat a high heat resistance of the pattern was maintained.

COMPARATIVE EXAMPLE 1

The same pattern formation and a pattern form observation as in Example1 were conducted except for using a photosensitive composition whichdoes not contain2-[2-(5-methylfurane-2-yl)ethenyl]-4,6-bis-(trichloromethyl)-s-triazineused as an acid generator in the composition of Example 1. The resultswere shown in Table 1. As shown in Table 1, a rectangular pattern wasformed after development without problems. However in this example thetop area became rounded by the post-baking at 120° C., the bottom of apattern began to flow to extend over at 140° C. and the lines werestacked together completely by flow of the pattern at 160° C. Asufficient heat resistance of the pattern was not obtained in thisexample.

COMPARATIVE EXAMPLE 2

The same pattern formation and a pattern form observation as in Example1 were conducted except for not conducting a whole area exposure tolight.

The results were shown in Table 1. As shown in Table 1, a rectangularpattern was formed after development without problems as almost the sameas Comparative Example 1. However in this example the top area becamerounded by the post-baking at 120° C., the bottom of a pattern began toflow to extend over at 140° C. and the lines were stacked togethercompletely by flow of the pattern at 160° C. A sufficient heatresistance of the pattern was not obtained in this example.

EXAMPLE 2

The same pattern formation and a pattern form observation as in Example1 were conducted except for replacing the photosensitizer and the photoacid generator of the photosensitive composition in Example 1 with thesubstance synthesized according to Synthesis Example 3 which is able tobe concurrently a photosensitizer and a photo acid generator. Theresults were shown in Table 1. As shown in Table 1, a rectangular shapewas maintained by baking at 120° C. and 140° C., and a top area becameslightly rounded at 160° C. as same as the result of Example 1. It wasconfirmed that a high heat resistance of the pattern was maintained inthis example. TABLE 1 after post- after post- after post- after bakingat baking at baking at development 120° C. 140° C. 160° C. Example - 1

Comparative Example - 1

Comparative Example - 2

Example - 2

EXAMPLE 3

The same pattern formation and a pattern form observation as in Example1 were conducted except for applying a light-exposure mask shown in FIG.1 which comprises a mask part composed by a 5 μm-width pattern and ahalf tone part composed by a 1.0 μm-width line and space patternabutting thereto. The line and space pattern of 1.0 μm formed as a halftone part was far below 3.0 μm (by a line and space) which was theguaranteed resolution limit by the manufacturer of Nikon's stepperFX-604F, that was a light-exposure device used for an exposure to light.The results were shown in Table 2. As shown in Table 2, the half tonepart was not resolved. Accordingly it provided with the sameeffectiveness as applying an exposure dose approximately by half, and apattern having the desired profile with the remaining film thickness ofa half height after development was formed. Besides no pattern formchange was observed after any post-baking at 120° C., 140° C. and 160°C. and it was confirmed that a half-tone type profile having asufficient heat resistance could be maintained.

COMPARATIVE EXAMPLE 3

A pattern formation and a pattern form observation were conducted in thesame manner as in Example 3 except for not conducting a whole areaexposure to light. The results were shown in Table 2. As shown in Table2, a half tone pattern was formed without problems as Example 3 afterdevelopment. However it flowed easily when being post-baked. As theresult the half tone part and a completely unexposed part were connectedto cause a profile which could not be applied for a half tone process.TABLE 2 after post- after post- after post- after baking at baking atbaking at development 120° C. 140° C. 160° C. Example - 3

Comparative Example - 3

EXAMPLE 4

When devising a mask design applying the thinking way of the half tonemask used in Example 3, a high heat resistant pattern having acorrugated form can be obtained. It means that a pattern formation and apattern form observation were conducted in the same manner as in Example3 except for applying a mask with a line and space part having aresolution of 2.5 μm which is slightly below 3.0 μm (by a line andspace) as the guaranteed resolution limit by the manufacturer of Nikon'sstepper FX-604F, that is a light-exposure device to be applied. Theresults were shown in Table 3. As shown in Table 3, the desiredcorrugated shaped pattern was obtained after development and thecorrugated form was not collapsed in post-baking after a whole areaexposure to light at each temperature of 120° C., 140° C. and 160° C.

COMPARATIVE EXAMPLE 4

A pattern formation and a pattern form observation were conducted in thesame manner as in Example 4 except for not conducting a whole areaexposure to light. The results were shown in Table 3. As shown in Table3, a corrugated form was formed without problems as was Example 4 afterdevelopment. However it flowed easily when being post-baked, and thecorrugated form could not be maintained. TABLE 3 after post- after post-after post- after baking at baking at baking at development 120° C. 140°C. 160° C. Example - 4

Comparative Example - 4

EFFECTS PF THE INVENTION

According to the present invention, it has become possible to form asuper high heat resistant pattern which has not been realized by thecomposition or the process so far applied. Therefore it is possible notonly to form a super high heat resistant pattern in a usual lithographybut also to form a pattern which is excellent in a heat resistance and adry-etching resistance in the specific applications such as a reservematerial of a half tone process or a corrugated form.

1. A pattern forming method comprising the steps of: [1] applying on a substrate material a photosensitive composition comprising (a) an alkali-soluble resin, (b) a photosensitizer having a quinone diazide group, (c) a photo acid generator, (d) a crosslinking agent and (e) a solvent to form a photosensitive layer; [2] a step of exposing the photosensitive layer in light through a mask; [3] removing said exposed area by development to form a positive image; and exposing a whole area of the positive image to light.
 2. The pattern forming method according to claim 1 wherein (b) the photosensitizer having a quinone diazide group and (c) the photo acid generator have an absorption activity at the same exposure wavelength and the whole area exposure is conducted at the exposure wavelength where both the photosensitizer and the photo acid generator have an absorption activity.
 3. A pattern forming method comprising the steps of: [1]applying on a substrate material a photosensitive composition comprising (a) an alkali-soluble resin, (f) a compound having a quinone diazide group and functioning as a photosensitizer and a photo acid generator, (d) a crosslinking agent and (e) a solvent to form a photosensitive layer; [2] exposing the photosensitive layer in light through a mask; [3] removing said exposed area by development to form a positive image; and [4] exposing a whole area of the positive image to light.
 4. The pattern forming method according to claim 1, which further comprises step [5] heat treatment (post-baking) which is carried out after the whole area exposure step.
 5. A pattern forming method according to claim 1, wherein (a) the alkali-soluble resin is at least one species selected from the group consisting of novolak resin, polyvinyl phenolic resins and acrylic resins.
 6. A pattern forming method according to claim 1, wherein the mask used in [2] the exposure step is a mask having a half-tone region which is partially made 10 to 90% of transmittance at a light transmission region being equipped with a semi-transparent film or installing a slit or a mesh having a dimension of not more than a resolution of the exposure device.
 7. The pattern forming method according to claim 2, which further comprises step [5] heat treatment (post-baking) which is carried out after the whole area exposure step.
 8. The pattern forming method according to claim 3, which further comprises step [5] heat treatment (post-baking) which is carried out after the whole area exposure step.
 9. A pattern forming method according to claim 2, wherein (a) the alkali-soluble resin is at least one species selected from the group consisting of novolak resin, polyvinyl phenolic resins and acrylic resins.
 10. A pattern forming method according to claim 3, wherein (a) the alkali-soluble resin is at least one species selected from the group consisting of novolak resin, polyvinyl phenolic resins and acrylic resins.
 11. A pattern forming method according to claim 4, wherein (a) the alkali-soluble resin is at least one species selected from the group consisting of novolak resin, polyvinyl phenolic resins and acrylic resins.
 12. A pattern forming method according to claim 2, wherein the mask used in [2] the exposure step is a mask having a half-tone region which is partially made 10 to 90% of transmittance at a light transmission region being equipped with a semi-transparent film or installing a slit or a mesh having a dimension of not more than a resolution of the exposure device.
 13. A pattern forming method according to claim 3, wherein the mask used in [2] the exposure step is a mask having a half-tone region which is partially made 10 to 90% of transmittance at a light transmission region being equipped with a semitransparent film or installing a slit or a mesh having a dimension of not more than a resolution of the exposure device.
 14. A pattern forming method according to claim 4, wherein the mask used in [2] the exposure step is a mask having a half-tone region which is partially made 10 to 90% of transmittance at a light transmission region being equipped with a semi-transparent film or installing a slit or a mesh having a dimension of not more than a resolution of the exposure device.
 15. A pattern forming method according to claim 5, wherein the mask used in [2] the exposure step is a mask having a half-tone region which is partially made 10 to 90% of transmittance at a light transmission region being equipped with a semi-transparent film or installing a slit or a mesh having a dimension of not more than a resolution of the exposure device. 